I've got what I believe to be an ornamental version of a pistol dagger that I picked up in Italy.
There's the emei piercers, hook sword and meteor hammer popular in Chinese martial arts. I believe somebody linked to deerhorn blades earlier in the thread.
The Indians made use of the chakram which is again fairly unusual.
On the western side of things, I believe there were multi-bladed swords (that is, swords with additional blades mounted in parallel), but I'm unsure as to the historical accuracy of such things.
I know they look common to us now, but boomerangs are really odd compared to most other thrown weapon.